Обсуждение: Integrated perc 5/i

Hi

I wanted to know if the integrated perc 5/i which come with Dell 2950 will yield maximum performance from RAID 10 ( 15K SAS ).
Or should I ask for different card ?

I read an old post that shows that RAID 10 does not work eficently under perc 5/i
http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&q=perc+5%2Fi+performance&rnum=6&hl=en#38837995887b6033

Does any one have any experience with RAID 10 & perc 5/i ?

Thanks,
Miki

--
--------------------------------------------------
Michael Ben-Nes - Internet Consultant and  Director.
http://www.epoch.co.il - weaving the Net.
Cellular: 054-4848113
--------------------------------------------------

On 8/16/07, Michael Ben-Nes <miki@epoch.co.il> wrote:
> Hi
>
> I wanted to know if the integrated perc 5/i which come with Dell 2950 will
> yield maximum performance from RAID 10 ( 15K SAS ).
> Or should I ask for different card ?
>
> I read an old post that shows that RAID 10 does not work eficently under
> perc 5/i
>
http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&q=perc+5%2Fi+performance&rnum=6&hl=en#38837995887b6033
>
> Does any one have any experience with RAID 10 & perc 5/i ?

no, I've tested raid 10 on a few different perc 5/i and never had
those results. raid 10 often gives poor sequential read performance
relative to a raid 5 but better random performance generally, which is
usually more important.  That said, the perc 5/e (never done raid 5 on
the 5/i) has posted some of the best raid 5 numbers I've ever seen in
terms of random performance on sata.

merlin

On Thu, Aug 16, 2007 at 11:26:52AM +0300, Michael Ben-Nes wrote:
> Does any one have any experience with RAID 10 & perc 5/i ?

Without having done PostgreSQL benchmarking, we have a 2950 with four SATA
disks in RAID 10 (and two SAS disks in RAID 1), and have not seen any
performance issues.

/* Steinar */
--
Homepage: http://www.sesse.net/

Thanks for all the answers.
It seems its a capable card.
Did any one changed the default stripe of 128kb ?





--
--------------------------------------------------
Michael Ben-Nes - Internet Consultant and  Director.
http://www.epoch.co.il - weaving the Net.
Cellular: 054-4848113
--------------------------------------------------

Hi Michael,

There is a problem with some Dell “perc 5” RAID cards, specifically we’ve had this problem with the 2950 as of 6 months ago – they do not support RAID10.  They have a setting that sounds like RAID10, but it actually implements spanning of mirrors.  This means that you will not get more than one disk worth of performance whether you are performing random seeks (within a one disk sized area) or sequential transfers.

I recommend you read the section in the Dell configuration guide very carefully and look for supplemental sources of technical information about it.  We found the issue clearly explained in a Dell technical memo that I don’t have in front of me – we were shocked to find this out.

As suggested – the RAID5 numbers from these controllers are very strong.

- Luke


On 8/16/07 1:26 AM, "Michael Ben-Nes" <miki@epoch.co.il> wrote:

Hi

I wanted to know if the integrated perc 5/i which come with Dell 2950 will yield maximum performance from RAID 10 ( 15K SAS ).
Or should I ask for different card ?

I read an old post that shows that RAID 10 does not work eficently under perc 5/i
http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&q=perc+5%2Fi+performance&rnum=6&hl=en#38837995887b6033  <http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&amp;q=perc+5%2Fi+performance&amp;rnum=6&amp;hl=en#38837995887b6033>

Does any one have any experience with RAID 10 & perc 5/i ?

Thanks,
Miki

On Thu, Aug 16, 2007 at 10:53:00AM -0700, Luke Lonergan wrote:
> They have a setting that sounds like RAID10, but it actually
> implements spanning of mirrors.

That's interesting. I'm pretty sure it actually says "RAID10" in the BIOS,
but is this a lie?

/* Steinar */
--
Homepage: http://www.sesse.net/

On Thu, Aug 16, 2007 at 07:59:15PM +0200, Steinar H. Gunderson wrote:
> On Thu, Aug 16, 2007 at 10:53:00AM -0700, Luke Lonergan wrote:
> > They have a setting that sounds like RAID10, but it actually
> > implements spanning of mirrors.
>
> That's interesting. I'm pretty sure it actually says "RAID10" in the BIOS,
> but is this a lie?

Unless they use the "plus notation" (ie: RAID 1+0 or RAID 0+1), you
never truly know what you're getting.

BTW, there's other reasons that RAID 0+1 stinks, beyond just
performance.
--
Decibel!, aka Jim Nasby                        decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

Hi

I wanted to know if the integrated perc 5/i which come with Dell 2950 will yield maximum performance from RAID 10 ( 15K SAS ).
Or should I ask for different card ?

I read an old post that shows that RAID 10 does not work eficently under perc 5/i
http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&q=perc+5%2Fi+performance&rnum=6&hl=en#38837995887b6033

Does any one have any experience with RAID 10 & perc 5/i ?

Thanks,
Miki

--
--------------------------------------------------
Michael Ben-Nes - Internet Consultant and  Director.
http://www.epoch.co.il - weaving the Net.
Cellular: 054-4848113
--------------------------------------------------

On 8/16/07, Luke Lonergan <llonergan@greenplum.com> wrote:
>
>  Hi Michael,
>
>  There is a problem with some Dell "perc 5" RAID cards, specifically we've
> had this problem with the 2950 as of 6 months ago – they do not support
> RAID10.  They have a setting that sounds like RAID10, but it actually
> implements spanning of mirrors.  This means that you will not get more than
> one disk worth of performance whether you are performing random seeks
> (within a one disk sized area) or sequential transfers.
>
>  I recommend you read the section in the Dell configuration guide very
> carefully and look for supplemental sources of technical information about
> it.  We found the issue clearly explained in a Dell technical memo that I
> don't have in front of me – we were shocked to find this out.

interesting.  this may also be true of the other 'rebrands' of the lsi
logic chipset.  for example, the ibm 8480/exp3000 sets up the same
way, namely you do the 'spanadd' function of the firmware which layers
the raids.

fwiw, I will be testing perc 5 raid 10, 01, 00, and 05 in a dual
controller controller configuration as well as dual controller
configuration over the md1000 (which is active/active) in a few days.
This should give very good support to your claim if the arrays spanned
in software singnificantly outperform a single controller.

merlin

On 8/16/07, tyrrill_ed@emc.com <tyrrill_ed@emc.com> wrote:
>
>
> Hi Miki,
>
> I am using a Dell 2950, and I recently switched from using RAID 5 of all six
> disks to three RAID 1 pairs with the OS on the first pair, postgres on the
> second except for pg_xlog, which I moved to the third pair.  This
> configuration change increased the insert performance of my application by
> 40%.  I have not tried RAID 10 so I cannot help you there.  My suggestion is
> test both RAID 5 and RAID 10, and report back to us what you find.

Good to know.

Also, be aware that one some RAID controllers, you'll get better
performance if you make the mirrors on the RAID controller, then RAID
0 them in the OS / Kernel.  RAID 0 is very low on overhead, so it
doesn't have much negative impact on the server anyway.  We have a
re-purposed Dell 4600 workstation with a single CPU and 2 Gigs ram
with a 4 disk linux kernel software RAID-10 that's quite a bit faster
at most db work than the 2850 w/ dual CPUs, 4 gigs ram, and a perc 5
series controller w/ battery backed cache and a 4 disk RAID-5 it is
complementing.

On Thu, Aug 16, 2007 at 01:30:11PM -0400, tyrrill_ed@emc.com wrote:
> Hi Miki,
> by 40%.  I have not tried RAID 10 so I cannot help you there.  My
> suggestion is test both RAID 5 and RAID 10, and report back to us what
> you find.

Unless you're running something like a data warehouse, I'd put a real
low priority on testing RAID5... it's rarely a good idea for a database.
--
Decibel!, aka Jim Nasby                        decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

Yay - looking forward to your results!

- Luke


On 8/16/07 3:14 PM, "Merlin Moncure" <mmoncure@gmail.com> wrote:

> On 8/16/07, Luke Lonergan <llonergan@greenplum.com> wrote:
>>
>>  Hi Michael,
>>
>>  There is a problem with some Dell "perc 5" RAID cards, specifically we've
>> had this problem with the 2950 as of 6 months ago ­ they do not support
>> RAID10.  They have a setting that sounds like RAID10, but it actually
>> implements spanning of mirrors.  This means that you will not get more than
>> one disk worth of performance whether you are performing random seeks
>> (within a one disk sized area) or sequential transfers.
>>
>>  I recommend you read the section in the Dell configuration guide very
>> carefully and look for supplemental sources of technical information about
>> it.  We found the issue clearly explained in a Dell technical memo that I
>> don't have in front of me ­ we were shocked to find this out.
>
> interesting.  this may also be true of the other 'rebrands' of the lsi
> logic chipset.  for example, the ibm 8480/exp3000 sets up the same
> way, namely you do the 'spanadd' function of the firmware which layers
> the raids.
>
> fwiw, I will be testing perc 5 raid 10, 01, 00, and 05 in a dual
> controller controller configuration as well as dual controller
> configuration over the md1000 (which is active/active) in a few days.
> This should give very good support to your claim if the arrays spanned
> in software singnificantly outperform a single controller.
>
> merlin